Osuna, who has 19 saves, did not appear in the ninth inning on Friday, when the Blue Jays surrendered four runs in a 5-4 walk-off loss to the Royals. Toronto manager John Gibbons said after the game that Osuna was unavailable because he wasn't feeling well.
Osuna made it clear on Saturday that his problem is not physical.
"I feel great physically," Osuna said. "It's just more mentally. It has been a couple of days that I have felt this way. I really don't know how to explain it. I just feel anxious. I feel like I am lost a little bit right now.